Thermosetting coating composition and coated body

ABSTRACT

The present invention intends to provide a thermosetting coating composition provided with workability, excellent adhesion, weatherability, good appearance, etc. capable of use in a primerless colored base coat and top clear coat by a 2-coat, 1-bake method on a polyolefinic substrate. Moreover, the present invention intends to provide a coated body having excellent adhesion, weatherability, good appearance, etc. realized by a 2-coat, 1-bake method. This thermosetting coating composition is a composition comprising a graft copolymer obtained by copolymerizing acrylic monomer, unsaturated carboxylic acids, acrylic monomers containing hydroxyl group with chlorinated polyolefin containing anhydride in the presence of organic solvents. This coating composition is available for use as a primerless colored base coat 2-coat, 1-bake coating on the polyolefinic substrates.

TECHNICAL FIELD

The present invention concerns a thermosetting coating composition. Morespecifically, it concerns a coating composition which is a coloursubstrate fit for polypropylene base such as a super high-strengthpolypropylene bumper substrate, etc. and which is capable of providingthe base material with excellent adhesion especially through two timescoating one time baking called "wet on wet system", made without primerby using this colour base and top clear coat and 1 bake (wet-on-wetsystem) and which is also capable of forming thermosetting coated filmhaving long-term weatherability, chemical resistance, waterproofing andhighly glossy and vivid coated film appearance.

BACKGROUND ART

Conventional coloured base coat for car body, which are generally madeof polyester, melamine, cellulose acetate butyrate resin ("CAB resin")or acrylic melamine resin, hardly have any adhesion to polyolefinicsubstrates consisting of so-called crystalline polyolefins with lowpolarity.

For that reason, paints containing modified or copolymerized chlorinatedpolyolefin containing anhydride are used as colored base coat for thecoating on polyolefinic substrates. Though they all have good adhesionto such substrates, these paints are used only for primer coating or1-coat top coating because of such problems as no hardening, pooradhesion or poor secondary adhesion after washing with water, etc.,which are vital problems for coating materials, in the coating made bythe method of directly coating a colour base having painting pigment andcompleting the coating with a single baking, i.e. primerless 2-coat1-bake system (wet on wet system of coloured base coat and top clearcoat).

Moreover, the paints containing modified or copolymerized chlorinatedpolyolefin containing anhydride which are supplied today are mostly oflacquer type or urethane crosslinking with polyisocyanate and of shortworking life and, therefore, it was practically very difficult to usethem by the primerless 2-coat, 1-bake method.

Furthermore, the coated film obtained had a defect of yellowingregarding long-term weatherability and problems such as poorwaterproofing, poor chemical resistance, etc. More specifically, theyhad a problem of producing dechlorination from polyolefinic substrateand modified chlorinated polyolefin containing anhydride, causingyellowing of aluminium pigment and top coat clear, etc.

As attempts for improving the polyolefinic substrate itself, varioustrials are being made such as plasma treatment (surface oxidation byoxygen plasma), frame treatment (surface oxidation by frame),ultraviolet ray treatment (furnishing of functionality by ultravioletray), etc. as measures for removing trichloroethane (improvement ofadhesion. However, those measures also have problems such as unstableadhesion, etc. depending on the kind of polyolefinic substrate (degreeof non polarity) and still remain in the stage of study. Moreover, whileit is possible to improve adhesion by introducing functional group intothe polyolefinic substrate, it makes the substrate costly.

Because of such defects, said formation of coated film is stillinsufficient in commercial value and has therefore not yet put topractical use. For that reason, the present invention intends to providea thermosetting coating composition provided with workability, excellentadhesion, weatherability, good appearance, etc. capable of primerlesscoloured base coat and top clear coat by a 2-coat, 1-bake method on thepolyolefinic substrates. Moreover, the present invention intends toprovide a coated body having excellent adhesion, weatherability, goodappearance, etc. realized by a 2-coat, 1-bake method.

DISCLOSURE OF THE INVENTION

In view of the current situation described above, the inventors of thepresent application assiduously made studies to solve said defects andfound that formation of coated film by primerless 2-coat, 1-bake methodfurnishing polyolefinic substrates with adhesion can be achievedproperly by dispersing the pigment in the paint with melamine resin andbridging it with acrylic copolymer which make graft copolymerizationwith chlorinated polyolefinic copolymer containing anhydride by means ofthis melamine resin under a thermal energy, and finally achieved thepresent invention.

Namely, the first to sixth inventions of the present application providea thermosetting coating composition comparing graft copolymer obtainedby copolymerizing acrylic monomers, unsaturated carboxylic acids,acrylic monomers containing hydroxyl group with chlorinated polyolefincontaining anhydride under organic solvent, and melamine resin andavailable for use as primerless coloured base coat of 2-coat 1-bakecoating on the polyolefinic substrates. Moreover, the 7th and 8thinventions of the present application provide coated bodies comprisingsubstrate coloured base coating on the surface of this substrate and topclear coat coating on the surface of this coloured base coat andrealized by the method of 2-coat 1-bake coating which consists inperforming baking after the coating of coloured base coat and top clearcoat, characterized in that this substrate is a polyolefinic basedmaterial with stable surface properties and that the coloured base coatis said thermosetting coating composition. It is desirable that thesubstrate be a bumper made of super high-strength polypropylene securingsufficient adhesion by washing with water.

Here, primerless coloured base coat of 2-coat 1-bake coating refers to apaint containing tinting pigment to be directly coated on polyolefinicsubstrate the coating of which is completed by coating a top clear coaton it by wet-on-wet system and making a single baking.

Said graft copolymer preferably comprises acrylic monomers representing30 to 94.5 wt % of total volume of whole monomers, unsaturatedcarboxylic acids representing 0.5 to 7.0 wt % of total volume of wholemonomers and acryilc monomers containing hydroxyl group representing 5to 25 wt % of total volume of whole monomers for chlorinated polyolefincontaining anhydride, and a number-average molecular weight ofapproximately 10,000 to 25,000.

Moreover, said melamine resin is butyl etherified melamine resin and thegraft copolymer to melamine resin ratio in solids content weight ispreferably 70-90 to 30-10.

Furthermore, a coated film formed on a polyolefinic substrate is liableto produce dechlorination from the polyolefinic substrate and theprimerless formation of thermosetting coated film and causedeterioration of clear coated film and pigment (aluminium) under theinfluence of C1 ions. For that reason, it is also desirable to make thecoating composition contain dechlorinating catcher such as basicmagnesium, basic aluminium (CO₃ ^(I) is easily displaced by C1), etc. todelay deterioration (yellowing of resin, discoloration of aluminium,storage stability). This dechlorinating catcher preferably represents0.5 to 2.5 wt % against the total solid content weight of said graftcopolymer and melamine resin.

In so-called metallic paints, etc., there are cases where aluminium iscontained in the paint. However, because ordinary aluminium deterioratesand causes discoloration and peeling by agglomeration under theinfluences of C1 ions brought about by said dechlorination, it isdesirable to use resin coated aluminium pigment as aluminium. This resincoated aluminium preferably represents 5 to 25 wt % for the total solidsby weight of said graft copolymer and melamine resin.

Still more, since polyolefinic substrates deteriorate very rapidly underthe influences of ultraviolet ray, it is desirable to contain anultraviolet ray absorber and a light stabilizer (in the paint) to delaydeterioration of the substrate.

The present invention will be described more in detail hereinbelow.

The coating composition of the present invention is realized by blendingmelamine resins (B) with graft copolymer (A) obtained by copolymerizingacrylic monomers containing hydroxyl group (e.g. (a-2), unsaturatedcarboxylic acids (e.g. (a-3)), acrylic monomers (e.g. (a-4)) withchlorinated polyolefin containing acid anhydride (e.g. (a-1)) in thepresence of an organic solvent and also blending a tinting pigment (F)as coloured base coat. Coated film is formed as a result of bridgingbetween the graft copolymer (A) and the melamine resins (B) producedwith baking under a thermal energy.

The solid content ratio of said chlorinated polyolefin (a-1) containinganhydride to said respective copolymers (a-2), (a-3), (a-4) shall beadjusted to 5:95 to 40:60 and more preferably to 10:90 to 20:80.

Moreover, the present invention intends to provide a method of formationof a thermosetting coated film realized by blending a dechlorinatingcatcher (C), resin coated aluminium (D) and ultraviolet ray absorber &light stabilizer (E) for the said solid content ratio of (A) and (B).

Here, polyolefin with a chlorination ratio of 40% or under, preferably15 to 30%, is desirable as said chlorinated polyolefin (a-1). Toenumerate only those which are particularly representative as suchpolyolefin, we may give the names of ethylene, propylene,ethylene-propylene copolymer, 1-butene, propylene-butene copolymer,ethylene-α-olefin copolymer, propylene-butadine copolymer, etc.Particularly desirable among them are propylene and ethylene-α-olefincopolymer, and we may cite copolymers chlorinated with carbontetrachloride, etc. for acid modified polyolefins such as maleicanhydride, citraconic anhydride, itaconic anhydride, etc. as unsaturatedcarboxylic acids. As for proportion of this chlorinated polyolefin, 15to 30% is most desirable because no transparent coated film uniform insolubility with melamine resins can be obtained and the adhesion dropsin case the rate of chlorination exceeds 40%.

Furthermore, to enumerate only those which are particularlyrepresentative as said acrylic monomers (a-2) containing hydroxyl groupsare 2-hydroxy ethyl (meth) acrylate, 2-hydroxy propyl meth acrylate,3-hydroxy propyl meth acrylate, 2-hydroxy butyl meth acrylate, 3-hydroxybutyl meth acrylate, 4-hydroxy butyl meth acrylate, etc. When thequantity of use of these acrylic monomers (a-2) containing hydroxylgroup is smaller than 5 wt %, solvent resistance, intercoat adhesion andchemical resistance are liable to become insufficient with a drop ofhardening capacity. On the other hand, when this quantity is larger than25%, adhesion with polyolefinic substrate and weatherability of coatedfilm, etc. are liable to drop. For that reason, it is desirable to keepthe quantity of use of these acrylic monomers (a-2) containing hydroxylgroup in the range of 5 to 25 wt % of the total weight of whole monomersor at a hydroxyl value (solid content) of 22.3 to 111.4, more preferably8 to 22 wt % of the total weight of whole monomers or at a hydroxylvalue (solid content) of 35.6 to 80.2.

Still more, to enumerate only those which are particularlyrepresentative as said unsaturated carboxylic acids (a-3) are methacrylic acid as unsaturated monocarboxylic acid and various kinds ofunsaturated monocarboxylic acids such as maleic acid anhydride, fumaricacid, itaconic acid, citraconic acid, mesaconic acid, etc. asunsaturated carboxylic acids. The quantity of use of these unsaturatedcarboxylic acids is 0.5 to 7.0 wt %, and any quantity of these compoundssmaller than 0.5 wt % leads to poor bridging with melamine resins,insufficient hardening capacity and poor gasoline resistance. On theother hand, if this quantity is larger than 7.0 wt %, the appearance andthe waterproofing of the coated film obtained drop and the storagestability also deteriorates. Therefore, this quantity shall preferablybe maintained in the range of 0.5 to 7.0 wt % of the total weight ofwhole monomers or at an acid value (solid content) of 3.8 to 53.4, morepreferably 1.0 to 3.0 wt % of the total weight of whole monomers or atan acid value (solid content) of 7.6 to 22.9.

Next, to enumerate only those which are particularly representative asacyclic monomers (a-4) copolymerizable with said (a-2), (a-3)respectively, are various kinds of (meth) acrylates such as methyl(meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate,i-propyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth)acrylate, tert-butyl (meth) acrylate, 2-ethyl-hexyl (meth) acrylate,lauryl (meth) acrylate, cyclo-hexyl (meth) acrylate, benzyl (meth)acrylate, dibromopropyl (meth) acrylate, tribromopropyl (meth) acrylate,aceto-acetoxyl ethyl (meth) acrylate, etc.

Furthermore, the solid content ratio of said chlorinated polyolefincontaining anhydride and acrylic copolymer (A) to melamine resins (B) is(A):(B)=70 to 90/30 to 10 wt %, preferably a solid content ratio of(A):(B)=75 to 85/25 to 15 wt %. Here, when (B) becomes 10 wt % or under,the waterproofing and the solvent resistance drop. On the other hand, if(B) is 30 wt % or over, the appearance and impact resistance will drop.

In addition, because the present invention is characterized in that thedispersion of pigment (F) in particular is made with melamine resins(B), it can naturally disperse pigments of low oil absorption quantitysuch as titanium oxide or iron dioxide based pigments. However, withpigments of poor dispersion and comparatively high oil absorptionquantity such as quinacridone pigments, phthalocyanine pigments andcarbon black which are organic pigments in particular, 20 to 25 % is aproper quantity of melamine resins (B) for securing good dispersion ofpigment without affecting the coated film performances.

Here, to enumerate only those which are particularly representative aspigments, are titanium dioxide as white pigment, iron oxideflavanthrone, azo isoindolinone, benzimidazolone, titanium oxide asyellow pigments, isoindolinone, iron oxide, indanthrene as orangepigments, perylene, monoazo, benzimidaazolone, quinacridone,anthroquinone, diketo pyrrole, indanthrene as red, phthalocyaninepigments, and azo as green pigment, carbon as black pigments, etc.

Moreover, said dechlorinating catcher may well be used in the range of0.5 to 2.0 wt % for the total solid content by weight of chlorinatedpolyolefin containing anhydride and acrylic copolymer (A) and melamineresins (B). While the effect becomes too large, the gloss and thewaterproofing drop if this quantity of use exceeds 2 wt %. To enumerateexamples of such dechlorinating catcher, are basic magnesium, aluminium,hydroxy, carbonate, hydrate, epoxy resin based materials. As typicalepoxy resin product, there is so-called bisphenol A type epoxy resin(epoxy equivalent 170 to 250, molecular weight 300 to 400) which is acondensate of bisphenol A and epichlor(o)hydrine.

Furthermore, said resin coated aluminium (D) may well be used in therange of 5 to 25 wt % for the total solids by weight of (A) and (B). Nodiscoloration or interfacial peeling due to deterioration of aluminiumare produced even with ordinary aluminium at a proportion under 5 wt %but the appearance quality deteriorates at over 25 wt %. To enumerateexamples of such resin coated aluminium, we may cite FZ or FM series(products of Toyo Aluminium K.K.), CR series (products of Asahi ChemicalMetals K.K.), etc.

Still more, said ultraviolet ray absorber and light stabilizer (E) maywell be used in the range up to 5 wt % for the total solids content byweight of (A) and (B). When they are used in excess of 5 wt %, thewaterproofing drops with occurrence of precipitation though the effectbecomes greater and it is also disadvantageous in respect of costs.

To enumerate examples of such ultraviolet ray absorber and lightstabilizer, we may cite as ultraviolet ray absorber3-[3-(2H-benzotriazol-2-yl)-5-t-butyl-A-hydroxyphenyl] benzotriazole,2-[2-hydroxy-3,5-bis (1,1-dimethylbenzyl) phenyl]-2H-benzotriazole,ethane diamide-N-(2-ethoxy phenyl)-N'-(4-isododexyl phenyl), etc.

As for light stabilizer, we may cite bis (2, 2, 6, 6-tetramethyl-1-octyl oxy-4-piperizyl) decanodioate, 1,3,8-triaza spiro (4, 5,)decane-2, 4-dione-8-acetyl-3; -dodecyl-7, 7, 9, 9-tetramer, 2, 2, 4,4-tetra methyl-20-(β-lauryl-oxycarbonyl)-ethyl-7-oxa-3, 20-diaza dispiro(5, 1, 11, 2) heneicosan-21-on, bis (1, 2, 2, 6,6-pentamethyl-4-piperidyl) sebacate, bis (1, 2, 2, 6,6-pentamethyl-4-piperidyl 1-2-butyl-2-(4-hydroxy-3, 5-di-tertiarybutylpenzyl) propanedioate, 2-(3-5-di-t-butyl-4-hydroxybenzyl)-2-n-butyl maronic acid bis (1, 2, 2, 6,6-pentamethyl-4-piperidyl), bis (1, 2, 2, 6, 6-pentamethyl-4-piperidyl)sebacate, etc.

Yet more, as a top clear coat coated on said coloured base coat, one mayselect as desired a product which is usually used for 2-coat, 1-bakecoatings and we may cite a thermosetting top clear coating based onacrylic melamine, fluorocarbon resin, silicon modified acrylic clear,acid-epoxy curing resin, acrylic resin, oil-free polyester resin,aminoalkyl resin, 2-part acrylic urethane, 2-part fluorocarbon modifiedurethane resin, 2-part silicon modified urethane, etc.

PREFERRED EXAMPLE OF THE INVENTION

Next, the present invention will be explained concretely with examplesand references. All parts and percentages given there are those inweight.

EXAMPLE 1

Put 500 parts of chlorinated polyolefin containing anhydride obtained bychlorinating maleic anhydride with carbon tetrachloride; rate ofchlorination=24%, solid content=30% (or under, hereinafter indicatedsimply as chlorinated polyolefin containing anhydride in this exampleand tables) and 850 parts of toluene in a 4-neck reaction vessel flaskequipped with agitator, thermometer and cooler, maintain the temperatureinside the flask at 75° to 85° C., and drip in it a mixture consistingof 450 parts of isobutyl meth-acrylate, 250 parts of cyclohexylmeth-acrylate, 130 parts of acrylic acid-2-hydroxyl ethyl and 20 partsof acrylic acid and a solution obtained by melting 5 parts of benzoylperoxide and 5 parts of azobisisobutyrnitrile in 300 parts of toluenefor 3 hours, and maintain for another 10 hours at the same temperatureeven after the end of dripping to let continue the reaction.

From this, we got a chlorinated polypropylene modified acrylic resinwith a non-volatile content of 40.4% and a number-average molecularweight of 18,000 (Example 1). Table 1 indicates those results.

Moreover, Table 1 also indicates products of the same composition withsaid example 1 but with different loads as examples 2 to 7. In theexplanation given hereafter, specific chlorinated polyolefin containinganhydride and acrylic copolymers of examples 1 to 7 will be abbreviatedas chlorinated polyolefin and acrylic copolymers (A1) to (A7).

                                      TABLE 1                                     __________________________________________________________________________                 Example 1                                                                           Example 2                                                                           Example 3                                                                           Example 4                                                                           Example 5                                                                           Example 6                                                                           Example                      __________________________________________________________________________                                                     7                            Chlorinated polyolefin                                                        and acrylic copolymers                                                        Chlorinated  500   500   500   500   500   330   1000                         polyolefin                                                                    containing                                                                    anhydride                                                                     Toluene      850   850   850   850   850   970   500                          Isobutyl     450   460   440   480   420   480   350                          (meth)-acrylate                                                               Cyclohexyl   250   250   250   270   230   270   200                          (meth)-acrylate                                                               2-hydroxy ethyl                                                                            130   130   130   80    180   130   130                          (meth)-acrylate                                                               Acrylic acid 20    10    30    20    20    20    20                           Benzoyl      5     5     5     5     5     5     5                            peroxide                                                                      Azobisisobuty-                                                                             5     5     5     5     5     5     5                            ronitrile                                                                     Toluene      300   300   300   300   300   300   300                          Total        2510  2510  2510  2510  2510  2510  2510                         Type name    A-1   A-2   A-3   A-4   A-5   A-6   A-7                          Non-volatile content (%)                                                                   40.2  40.2  40.2  40.2  40.2  40.2  40.2                         Molecular weight (MN)                                                                      17000 17000 18000 19000 16000 17000 17000                        Hydroxyl group value                                                                       57.9  57.9  57.9  35.6  80.2  57.9  57.9                         (solid contents)                                                              Acid value   15.2  7.6   22.9  15.2  15.2  15.2  15.2                         (solid contents)                                                              __________________________________________________________________________

Next, we obtain various kinds of coloured base coat by dispersing 60.18parts of these chlorinated polyolefin and acrylic copolymers (A1) to(A7), 13.37 parts of butylated melamine resin (B) and 0.90 parts ofdechlorinating catcher (C) in advance with a sand mill and thenagitating and dispersing 800 parts of resin coated aluminium (B) and0.90 and 0.45 parts respectively of ultraviolet ray absorber and lightstabilizer with the agitator. Table 2 indicates those coloured basecoats.

                                      TABLE 2                                     __________________________________________________________________________    Name of type of                                                               coloured base coats                                                                      A-1 A-2                                                                              A-3                                                                              A-4                                                                              A-5                                                                              A-6                                                                              A-7                                                                              A-8 A-9                                      __________________________________________________________________________    Polyolefin acrylic                                                                       60.18                                                                             ←                                                                           ←                                                                           ←                                                                           ←                                                                           ←                                                                           ←                                                                           ←                                                                            ←                                   graft copolymer                                                               containing anhydride                                                          (40%)                                                                         Butylated melamine                                                                       13.37                                                                             ←                                                                           ←                                                                           ←                                                                           ←                                                                           ←                                                                           ←                                                                           ←                                                                            ←                                   resin (60%)                                                                   Resin coated                                                                             8.00                                                                              ←                                                                           ←                                                                           ←                                                                           ←                                                                           ←                                                                           ←                                                                           ←                                                                            None                                     aluminium                                                                     Dechlorinating                                                                           0.90                                                                              ←                                                                           ←                                                                           ←                                                                           ←                                                                           ←                                                                           ←                                                                           None                                                                              0.90                                     catcher                                                                       UVA        0.90                                                                              ←                                                                           ←                                                                           ←                                                                           ←                                                                           ←                                                                           ←                                                                           ←                                                                            ←                                   HALS       0.45                                                                              ←                                                                           ←                                                                           ←                                                                           ←                                                                           ←                                                                           ←                                                                           ←                                                                            ←                                   Additive (Dispersing                                                                     8.00                                                                              ←                                                                           ←                                                                           ←                                                                           ←                                                                           ←                                                                           ←                                                                           ←                                                                            ←                                   agent RC)                                                                     Flow levelling agent                                                                     0.20                                                                              ←                                                                           ←                                                                           ←                                                                           ←                                                                           ←                                                                           ←                                                                           ←                                                                            ←                                   Solvent    8.00                                                                              ←                                                                           ←                                                                           ←                                                                           ←                                                                           ←                                                                           ←                                                                           8.90                                                                              8.00                                     Ordinary aluminium                                                                       None                                                                              ←                                                                           ←                                                                           ←                                                                           ←                                                                           ←                                                                           ←                                                                           ←                                                                            8.00                                     Total      100.00                                                                            ←                                                                           ←                                                                           ←                                                                           ←                                                                           ←                                                                           ←                                                                           ←                                                                            ←                                   __________________________________________________________________________

Example 1 to 7 correspond to coloured base coat types A-1 to A-7 (typename). However, coloured base coats type A-8 is a case where nodechlorinating catcher is used for example 1, while coloured base coattype A-9 is a case where ordinary aluminium is used in substitution forresin coated aluminium for example 1. After that, the respectivecoloured base coats are coated in the following process:

Process 1: Submitted super high-strength polypropylene bumper substrate(70×150×20 mm) to surface treatment by washing with water.

Process 2: Next, after coating this substrate by spraying the coatingcompositions (coloured base coat) of examples 1 to 7 to a film thicknessof 15 μ respectively, left the materials under normal temperature for 4minutes for flushing.

Process 3: Further coat Elastometric 2000 Clear (thermosetting solventtype paint consisting of acrylic copolymer and melamine resin) of T B LCo., Ltd. on this wet coat film by spraying to a film thickness of 30 μand, after 10 minutes of setting, performed baking at 120° C. for 30minutes. Table 3 indicates the results of evaluation of such products.

                                      TABLE 3                                     __________________________________________________________________________    Name of type of                                                               coloured base coat                                                                        A-1                                                                              A-2                                                                              A-3                                                                              A-4                                                                              A-5 A-6                                                                              A-7                                                                              A-8                                                                              A-9                                      __________________________________________________________________________    Substrate   Super high-strength polypropylene bumper substrate                            (surface treatment by washing with water)                         Baking conditions                                                                         Bake at 120° C. for 30 minutes.                            Results of Evaluation                                                         Primary adhesion                                                                           100/100                                                                         ←                                                                           ←                                                                           ←                                                                           ←                                                                            ←                                                                           ←                                                                           ←                                                                           ←                                   (Evaluation    ←                                                                           ←                                                                           ←                                                                           ←                                                                            ←                                                                           ←                                                                           ←                                                                           ←                                   of adherence)                                                                 Secondary adhesion                                                            Evaluation   100/100                                                                         ←                                                                           ←                                                                           ←                                                                           ←                                                                            ←                                                                           ←                                                                           ←                                                                           ←                                   of adherence   ←                                                                           ←                                                                           ←                                                                           ←                                                                            ←                                                                           ←                                                                           ←                                                                           ←                                   after                                                                         moisture                                                                      resistance                                                                    Evaluation   100/100                                                                         ←                                                                           ←                                                                           ←                                                                           ←                                                                            ←                                                                           ←                                                                           ←                                                                           ←                                   of adherence   ←                                                                           ←                                                                           ←                                                                           ←                                                                            ←                                                                           ←                                                                           ←                                                                           ←                                   after hot                                                                     water                                                                         resistance                                                                    Evaluation of heat                                                                        ◯                                                                    ←                                                                           ←                                                                           ←                                                                           ←                                                                            ←                                                                           ←                                                                           Δ                                                                          Δ                                  resistance                                                                    Evaluation of                                                                             ◯                                                                    ←                                                                           ←                                                                           ←                                                                           ←                                                                            ←                                                                           ←                                                                           ←                                                                           ←                                   storage stability                                                             Evaluation of                                                                             ◯                                                                    ←                                                                           ←                                                                           ←                                                                           ←                                                                            ←                                                                           ←                                                                           ←                                                                           ←                                   workability                                                                   Evaluation of                                                                             ◯                                                                    ←                                                                           ←                                                                           ←                                                                           ←                                                                            ←                                                                           ←                                                                           ←                                                                           ←                                   gasoline resistance                                                           __________________________________________________________________________

Next, explain references for comparison, we obtained chlorinatedpolyolefin and acrylic copolymers in the same way as in example 1,except that the polymerizing conditions were changed as shown in Table 4and that chlorinated polyolefin, polymerization initiator and variouskinds of acrylic monomers were used in the presence of polymerizingsolvent as shown in Table 4. Table 4 indicates those conditions asreferences for comparison 1 to 6.

                                      TABLE 4                                     __________________________________________________________________________                 References                                                                          References                                                                          References                                                                          References                                                                          References                                                                          References                                      for com-                                                                            for com-                                                                            for com-                                                                            for com-                                                                            for com-                                                                            for com-                                        parison 1                                                                           parison 2                                                                           parison 3                                                                           parison 4                                                                           parison 5                                                                           parison 6                          __________________________________________________________________________    Chlorinated polyolefin                                                        and acrylic copolymers                                                        Chlorinated  167   1333  500   500   500   500                                polyolefin                                                                    containing                                                                    anhydride                                                                     Toluene      1083  267   850   850   850   850                                Isobutyl     510   290   460   420   500   370                                meth-acrylate                                                                 Cyclohexyl   290   160   225   230   280   210                                meth-acrylate                                                                 2-hydroxy ethyl                                                                            130   130   130   130   50    250                                meth-acrylate                                                                 Acrylic acid 20    20    5     70    20    20                                 Benzoyl      5     5     5     5     5     5                                  peroxide                                                                      Azobisisobuty-                                                                             5     5     5     5     5     5                                  ronitril                                                                      Toluene      300   300   300   300   300   300                                Total        2510  2510  2510  2510  2510  2510                               Type name    B-1   B-2   B-3   B-4   B-5   B-6                                Non-volatile content (%)                                                                   40.2  40.2  40.2  40.2  40.2  40.2                               Hydroxyl group value                                                                       57.9  57.9  35.6  80.2  22.3  111.4                              (solid contents)                                                              Acid value   15.2  15.2  3.8   53.4  15.2  15.2                               (solid contents)                                                              __________________________________________________________________________

After that, we obtained various kinds of coloured base coat in the sameway as in example 1, except that we changed polyolefin, acryliccopolymers, butylated melamine resin (B), dechlorinating catcher, resincoated aluminium, ultraviolet ray absorber and light stabilizerindicated in Table 5 under the conditions as indicated there at the sametime. Table 5 indicates those details. References for comparison 1 to 7correspond to different types of coloured base coat or B-1 to B-6 (typename).

                  TABLE 5                                                         ______________________________________                                        Name of type of                                                               coloured base coat                                                                          B-1     B-2    B-3  B-4  B-5  B-6                               ______________________________________                                        Polyolefin acrylic graft                                                                    60.18   ← ←                                                                             ←                                                                             ←                                                                             ←                            copolymer containing                                                          anhydride (40%)                                                               Butylated melamine                                                                          13.37   ← ←                                                                             ←                                                                             ←                                                                             ←                            resin (60%)                                                                   Resin coated aluminium                                                                      8.00    ← ←                                                                             ←                                                                             ←                                                                             ←                            Dechlorinating catcher                                                                      0.90    ← ←                                                                             ←                                                                             ←                                                                             ←                            UVA           0.90    ← ←                                                                             ←                                                                             ←                                                                             ←                            HALS          0.45    ← ←                                                                             ←                                                                             ←                                                                             ←                            Additive (Dispersing                                                                        8.00    ← ←                                                                             ←                                                                             ←                                                                             ←                            agent RC)                                                                     Flow levelling agent                                                                        0.20    ← ←                                                                             ←                                                                             ←                                                                             ←                            Solvent       8.00    ← ←                                                                             ←                                                                             ←                                                                             ←                            Ordinary aluminium                                                                          None    ← ←                                                                             ←                                                                             ←                                                                             ←                            Total         100.00  ← ←                                                                             ←                                                                             ←                                                                             ←                            ______________________________________                                    

Those references for comparison (coloured base coat types B-1 to B-6)were coated under the same conditions as example. The results ofevaluation are indicated in Table 6.

                  TABLE 6                                                         ______________________________________                                        Name of type of                                                               coloured base coat                                                                          B-1    B-2    B-3  B-4  B-5  B-6                                ______________________________________                                        substrate     Super high-strength polypropylene                                             bumper base material (surface treatment                                       by washing with water)                                          Baking conditions                                                                           Bake at 120° C. for 30 minutes.                          Results of Evaluation                                                         Primary adhesion                                                                             80/100                                                                               60/100                                                                               100/100                                                                            100/100                                                                            100/100                                                                            100/100                           (Evaluation                                                                   of adherence)                                                                 Secondary adhesion                                                            Evaluation     80/100                                                                               60/100                                                                               90/100                                                                             90/100                                                                             95/100                                                                             90/100                            of adherence                                                                  after                                                                         moisture                                                                      resistance                                                                    Evaluation     80/100                                                                               60/100                                                                               90/100                                                                             90/100                                                                             95/100                                                                             90/100                            of adherence                                                                  after hot                                                                     water                                                                         resistance                                                                    Evaluation of heat                                                                          ◯                                                                        Δ                                                                              ◯                                                                      ◯                                                                      ◯                                                                      ◯                      resistance                                                                    Evaluation of Δ                                                                              ◯                                                                        ◯                                                                      Δ                                                                            ◯                                                                      ◯                      storage stability                                                             Evaluation of ◯                                                                        Δ                                                                              ◯                                                                      ◯                                                                      ◯                                                                      ◯                      workability                                                                   Evaluation of ◯                                                                        Δ                                                                              Δ                                                                            ◯                                                                      Δ                                                                            ◯                      gasoline resistance                                                           ______________________________________                                    

As shown in Table 6, the coloured base coats of references forcomparison were all confirmed to be inferior to that of the example inrespect of adhesion. The evaluate them individually, B-1 is believed tohave deteriorated in adhesion because of improper chlorinated polyolefinto acrylic copolymer ratio. B-2 has poor compatibility with melaminebecause of improper chlorinated polyolefin to acrylic copolymer ratio.B-3 is poor in both low-temperature hardening capacity and gasolineresistance for reason of low oxidation. B-4 dropped in waterproofing andbecame poor in storage stability because of high oxidation. B-5 has poorintercoat adhesion due to low OH value. B-6 dropped in bothwaterproofing and hardening capacity because of high OH value.

As explained so far, the present invention can provide a thermosettingcoating composition demonstrating excellent adhesion to substrate in thecase where coloured base coat and top clear coat are coated onpolyolefinic substrate by 2-coat 1-bake method without primer and driedby baking.

Moreover, by containing dechlorinating catcher, the present inventioncan delay deterioration of coated film (yellowing of resin,discoloration of aluminium, instability during storage).

Furthermore, it can also prevent discoloration, peeling by agglomerationdue to deterioration of aluminium, by using resin coated aluminumpigment as aluminium.

Still more, it can prevent deterioration of substrate by containingultraviolet ray absorber and light stabilizer.

In this way, the present invention can provide an excellentthermosetting coating composition which can be coated on polyolefinicsubstrate by 2-coat, 1-bake method without primer, providing excellentlong-term weatherability, durability as well as coated film appearancewith excellent gloss and vividness.

Yet more, the 7th and 8th inventions of the present application canprovide painted body having excellent adhesion, weatherability, goodappearance, etc. realized by 2-coat 1-bake method coated on polyolefinicsubstrate by 2-coat 1-bake method without primer.

We claim:
 1. A thermosetting coating composition comprising a graftcopolymer obtained by copolymerizing acrylic monomers, unsaturatedcarboxylic acids, acrylic monomers containing hydroxyl group withchlorinated polyolefin containing anhydride in the presence of anorganic solvent phase, and melamine resin, which is available for use asa primerless coloured base coat of a 2-coat, 1-bake coating for apolyolefinic substrate.
 2. A thermosetting coating composition asdefined in claim 1, wherein said graft copolymer comprises acrylicmonomers representing 30% to 94.5 wt % of total volume of wholemonomers, unsaturated carboxylic acids representing 0.5 to 7.0 wt % oftotal volume of whole monomers and acrylic monomers containing hydroxylgroup representing 5 to 25 wt % of total volume of whole monomers ofchlorinated polyolefin containing acid anhydride, and a number-averagemolecular weight of approximately 10,000 to 25,000.
 3. A thermosettingcoating composition as defined in claim 1, wherein said melamine resinis butyl etherified melamine resin and the graft copolymer to melamineresin ratio in solids content by weight is 70-90 to 30-10.
 4. Athermosetting coating composition as defined in claim 1, wherein thecoating composition contains dechlorinating catcher representing 0.5 to2.5 wt % for the total solids by weight of said graft copolymer andmelamine resin.
 5. A thermosetting coating composition as defined inclaim 1, wherein the coating composition contains resin coated aluminumrepresenting 5 to 25 wt % for the total solids by weight of said graftcopolymer and melamine resin.
 6. A thermosetting coating composition asdefined in claim 1, wherein the coating composition contains anultraviolet ray absorber and a light stabilizer.
 7. A coated bodycomprising a substrate, a coloured base coat coated on the surface ofsaid substrate and a top clear coat coated on the surface of saidcoloured base coat and produced by a 2-coat, 1-bake method whichcomprises coating of said coloured base coat and said top clear coat onsaid substrate, and baking said substrate having said coatings thereon,wherein said substrate is a polyolefinic based material having stablesurface properties and said coloured base coat is said thermosettingcoating composition of claim
 1. 8. A coated body comprising a substrateas defined in claim 7, wherein the substrate is a bumper made of superhigh-strength polypropylene securing sufficient adhesion by washing withwater.
 9. A thermosetting coating composition as defined in claim 1,wherein said thermosetting coating composition is baked at at least 120°C.
 10. A thermosetting coating composition as defined in claim 7,wherein said thermosetting coating composition is baked at at least 120°C.
 11. A thermosetting coating composition as defined in claim 1, whichhas a number-average molecular weight of approximately 10,000 to 25,000.12. A thermosetting coating composition as defined in claim 7, which hasa number-average molecular weight of approximately 10,000 to 25,000. 13.A thermosetting coating composition as defined in claim 1, wherein theacrylic monomers are selected from the group consisting of methyl (meth)acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl(meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate,tert-butyl (meth) acrylate, 2-ethyl-hexyl (meth) acrylate, lauryl (meth)acrylate, cyclo-hexyl (meth) acrylate, benzyl (meth) acrylate,dibromopropyl (meth) acrylate, tribromopropyl (meth) acrylate andaceto-acetoxyl ethyl (meth) acrylate.
 14. A thermosetting coatingcomposition as defined in claim 1, wherein said unsaturated carboxylicacids are an unsaturated monocarboxylic acid.
 15. A thermosettingcoating composition as defined in claim 1, wherein said acrylic monomerscontaining hydroxyl group is selected from the group consisting of2-hydroxyl ethyl (meth) acrylate, 2-hydroxy propyl (meth) acrylate,3-hydroxy propyl (meth) acrylate, 2-hydroxy butyl (meth) acrylate,3-hydroxy butyl (meth) acrylate and 4-hydroxy butyl (meth) acrylate. 16.A thermosetting coating composition as defined in claim 1, wherein thepolyolefin of said chlorinated polyolefin containing anhydride isethylene, propylene, ethylene-propylene copolymer, 1-butene,propylene-butene copolymer, ethylene-α-olefin copolymer andpropylene-butadine copolymer, wherein the chlorination ratio is 15-30%.17. A coated body comprising a substrate, a coloured base coat coated onthe surface of said substrate and a top clear coat coated on the surfaceof said coloured base coat and produced by a 2-coat, 1-bake method whichcomprises coating of said coloured base coat and said top clear coat onsaid substrate, and baking said substrate having said coatings thereonat at least 120° C., wherein said substrate is a polyolefinic basedmaterial having stable surface properties and said coloured base coat issaid thermosetting coating composition of claim 2.